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MathGroup Archive 1999

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Re: Finding real part (newbie question)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15770] Re: [mg15722] Finding real part (newbie question)
  • From: Carl Woll <carlw at fermi.phys.washington.edu>
  • Date: Sun, 7 Feb 1999 02:03:51 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Gnalle,

The mathematica function you are looking for is ComplexExpand. For
example,

ComplexExpand[ Re[1/(a + I b + 1/(c + I d))], TargetFunctions->{Re,Im}]

The option TargetFunctions->{Re,Im}

is not necessary, but it usually helps produce the output you are
looking for. Without this option, Mathematica will think that Abs[a+b
I] does not need to be simplified/expanded.

You might also want to throw in a Simplify[] command on your output.

Carl Woll
Dept of Physics
U of Washington

On Fri, 5 Feb 1999, Gnalle wrote:

> If a,b,c,d are real numbers. How do I use mathematica to find the real
> part of
> 
> 1/(a + I b + 1/(c + I d))
> 
> Yes I can calculate it by hand, but I would like to know how to use
> Mathematica.
> -- 
> 
> 			Niels Langager Ellegaard	
> 			'http://mmf.ruc.dk/~gnalle/'
> 



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